/Engine/Plugins/MeshPainting/Source/MeshPaintingToolset/Public/MeshPaintHelpers.h
Given the adapter, settings and view-information retrieves influences triangles and applies Action to them
bool ApplyPerTrianglePaintAction ( [IMeshPaintComponentAdapter](API\Plugins\MeshPaintingToolset\IMeshPaintComponentAdapter) * Adapter, const FVector & CameraPosition, const FVector & HitPosition, const [UBrushBaseProperties](API\Runtime\InteractiveToolsFramework\BaseTools\UBrushBaseProperties) * Settings, FPerTrianglePaintAction Action, bool bOnlyFrontFacingTriangles )